Ultrasound by Sunil

Therapeutic ultrasound and application, physiotherapy based application of ultrasound, for basic understanding of ultrasound and its uses for therapeutic purpose.

1. ULTRASOUND
A Deep Thermal & Non-thermal
Mechanical Modality
Made by
SUNIL
MPT, (C.P.R.S )
J. M. I

2. Ultrasound
•May be used for diagnostic imaging,
therapeutic tissue healing, or tissue destruction
•Thermal & Non-thermal effects
•Can deliver medicine to subcutaneous tissues
(phonophoresis)

3. Ultrasound
•Sinusoidal waveform
–Therapeutic ultrasound waves range from 750,000
to 3,000,000 Hz (0.75 to 3 MHz)
•Displays properties of
–wavelength,
–frequency,
–Amplitude

4. Transducer
•A device that converts one form of energy to another
•Piezoelectric crystal: a crystal that produces (+) and (-)
electrical charges when it contracts or expands
–Crystal of quartz, barium titanate, lead zirconate, or titanate
housed within transducer
•Reverse (indirect) piezoelectric effect: occurs when an
alternating current is passed through a crystal resulting in
contraction & expansion of the crystal
–US is produced through the reverse piezoelectric effect
–Vibration of crystal results in high-frequency sound waves
•Fresnal zone (near field) – area of the ultrasound beam on
the transducer used for therapeutic purposes

5. Longitudinal vs. Transverse Waves
•Longitudinal waves – molecular displacement is
along direction in which waves travel (bungee
cord)
–Compression – regions of high molecular density
(molecules in high pressure areas compress)
–Rarefraction – regions of low molecular density
(molecules in low pressure areas expand)
•Transverse waves – molecular displacement in
direction perpendicular to wave (guitar string)

6. •Longitudinal waves – travel in solids & liquids
–Soft tissue – more like liquids
–US primarily travels as longitudinal wave
•Transverse waves – cannot pass through
fluids; found in the body only when
ultrasound strikes bone

7. Frequency
•Frequency: number of times an event occurs in
1 second; expressed in Hertz or pulses per
second
–Hertz: cycles per second
–Megahertz: 1,000,000 cycles per second
•In the U.S., we mainly use ultrasound frequencies of 1, 2
and 3 MHz
•1 = low frequency; 3 = high frequency
•¯ frequency = ­ depth of penetration
•­ frequency = sound waves are absorbed in
more superficial tissues (3 MHz)

8. Velocity
•The speed of sound wave is directly related to the
density (­ velocity = ­ density)
•Denser & more rigid materials have a higher velocity
of transmission
•At 1 MHz, sound travels through soft tissue @ 1540
m/sec and 4000 m/sec through compact bone

9. Influences on the Transmission of Energy
•Reflection – occurs when the wave can’t pass
through the next density
•Refraction – is the bending of waves as a result
of a change in the speed of a wave as it enters a
medium with a different density
•Absorption – occurs by the tissue collecting the
wave’s energy

10. Attenuation
•Decrease in a wave’s intensity resulting from absorption,
reflection, & refraction
–­ as the frequency of US is ­ because of molecular friction the waves
must overcome in order to pass through tissues
•US penetrates through tissue high in water content & is
absorbed in dense tissues high in protein
•­ Absorption = ­ Frequency (3 MHz) , and
•­ Penetration = ¯ Absorption (1 MHz) , so
•­ Penetration = ¯ Frequency + ¯ Absorption (1 MHz)
•Tissues ­ water content = low absorption rate (fat)
•Tissues ­ protein content = high absorption rate (peripheral
nerve, bone)
–Muscle is in between both

11. Attenuation: Acoustic Impedance
•Determines amount of US energy reflected at tissue interfaces
–If acoustic impedance of the 2 materials forming the interface is the
same, all sound will be transmitted
–The larger the difference, the more energy is reflected & the less energy
that can enter the 2
nd
medium
•US passing through air = almost all reflected (99%)
•US through fat = 1% reflected
•Both reflected/refracted @ m. interface
•Soft-tissue: bone interfaced = much reflected
•As US energy is reflected @ tissue interfaces with different
impedances, intensity is increased creating a Standing Wave (hot
spot)

12. •Effective Radiating Area (ERA): area of the sound
head that produces ultrasonic waves; expressed in
square centimeters (cm
2
)
–Represents the portion of the head’s surface area that
produces US waves
–Measured 5 mm from face of sound head; represents all
areas producing more than 5% of max. power output
–Always lesser area than actual size of sound head
–Large diameter heads – column beam
–Small diameter heads – more divergent beam
–Low frequency (1 MHz) – diverge more than 3 MHz
•Treatment Duration: time for total treatment

13. Intensity Output & Power
•Power: measured in watts (W);
–amount of energy being produced by the transducer
•Intensity: strength of sound waves @ a given location
within the tissues being treated
•Spatial Average Intensity (SAI): amount of US
energy passing through the US head’s ERA;
–expressed in watts per square centimeter (W/cm
2
)
(power/ERA)
–Changing head size affects power density (larger head results
in lower density)
–Limited to 3.0 W/cm
2
of maximum output

14. Intensity Output & Power
•Spatial Average Temporal Peak Intensity (SATP):
average intensity during the “on” time of the pulse
–Output meter displays the SATP intensity
•Spatial Peak Intensity (SPI): max. output (power)
produced within an ultrasound beam
•Spatial Average Temporal Average Intensity (SATA) or
Temporal (time) Average Intensity:
–Power of US energy delivered to tissues over a given period of time
–Only meaningful for Pulsed US
–SAI x Duty Cycles

15. Beam Nonuniformity Ratio (BNR)
•Ratio between the spatial peak intensity (SPI)
to the average output as reported on the
unit’s meter
–The lower the BNR, the more uniform the beam is
–A BNR greater than 8:1 is unsafe
–Because of the existence of high-intensity areas in
the beam (hot spots), it is necessary to keep the
US head moving

16. Duty Cycle
•Percentage of time that US is actually being emitted
from the head
•Ratio between the US’s pulse length & pulse interval
when US is being delivered in the pulsed mode
–Pulse length = amount of time from the initial nonzero
charge to the return to a zero charge
–Pulse interval – amount of time between ultrasonic pulses
–Duty cycle = pulse length/(pulse length + pulse interval) x
100
–100% duty cycle indicates a constant US output
–Low output produces nonthermal effects (20%)

17. Movement of the Transducer
•4 cm
2
/sec
•Remaining stationary can cause problems
•Moving too rapidly decreases the total amount of
energy absorbed per unit area
–May cause clinician to treat larger area and the desired
temps. May not be attained
•Slower strokes can be easier maintained
•If patient complains of pain or excessive heat, then
decrease intensity but increase time
•Apply constant pressure – not too much & not too
little

18. Coupling Agents
•Optimal agent – distilled H
2
0 (.2% reflection)
•Modern units have a shut down mechanism if sound
head becomes too hot (Dynatron beeps; red lights on
Chattanoogas)
–Improperly coupled head causes ­ temp.
•Types of agents:
–Direct
–H
2
0 immersion
–Bladder
•Reduce amount of air bubbles

19. Direct Coupling
•Effectiveness is ¯ if body part is hair, irregular
shaped, or unclean
•Must maintain firm, constant pressure
•Various gels utilized

20. Water Immersion
•Used for odd shaped parts
•Place head approx. 1” away from part
•Operator’s hand should not be immersed No
metal on part or operator’s hand
•Ceramic tub is recommended
•If nondistilled H
2
0 is used, intensity can be ­ .5
w/cm
2
because of air & minerals
•Don’t touch skin except to briefly sweep skin
when bubbles form

21. Bladder
•H
2
0 filled balloon or plastic bag coated with
coupling gel
•Use on irregular shape part
•Place gel on skin, then place the bladder on
the part, and then place gel on bladder
•Make sure all air pockets are removed from
bladder

22. Indications
•Soft tissue healing & repair
•Joint contractures & scar tissue
•Muscle spasm
•Neuroma
•Trigger areas
•Warts
•Sympathetic nervous system disorders
•Postacute reduction of myositis ossificans
•Acute inflammatory conditions (pulsed)
•Has been shown to be ok to use following the
stopping of bleeding with an acute injury (pulsed)

23. Contraindications
•Acute conditions (continous output)
•Ischemic areas or impaired circulation areas
•Tendency to hemorrhage
•Around eyes, heart, skull, or genitals
•Over pelvic or lumbar areas in pregnant or
menstruating females
•Cancerous tumors
•Spinal cord or large nerve plexus in high doses
•Anesthetic areas
•Stress fracture sites or over fracture site before
healing is complete (continuous); epiphysis
•Acute infection

24. Thermal Effects
•­ blood flow
•­ sensory & motor nerve conduction velocity
•­ extensibility of structures (collagen); ¯ joint
stiffness
•­ collagen deposition
•­ macrophage activity
•Mild inflammatory response which may enhance
adhesion of leukocytes to damaged endothelial cells
•¯ muscle spasm
•¯ pain
•+ all Nonthermal effects

25. Nonthermal Effects
•­ cell membrane permeability
•­ vascular permeability
•­ blood flow
•­ fibroblastic activity
•Altered rates of diffusion across cell membrane
•Secretion of chemotactics
•Stimulation of phagocytosis
•Production of granulation tissue
•Synthesis of protein
•¯ edema
•Diffusion of ions
•Tissue regeneration
•Formation of stronger CT

26. Pulsed Ultrasound
•Stimulates phagocytosis (assists w/ ¯ of chronic
inflammation) & increases # of free radicals (­ ionic
conductance on cell membrane)
•Cavitation: formation of gas bubbles that expand &
compress due to pressure changes in tissue fluids
–Stable – occurs when bubbles compress during the ­-press.
peaks followed expansion of bubbles during ¯-press. troughs
–Unstable (transient) – compression of bubbles during ­-press.
Peaks, but is followed by total collapse during trough (BAD!)

27. Pulsed Ultrasound
•Acoustical Streaming: stable cavitation leads this; one-
directional flow of tissue fluids, & is most marked
around cell membranes
–Facilitates passage of calcium potassium & other ions, etc.
in/out of cells
–Collagen synthesis, chemotactics secretion, ­ update of
calcium in fibroblasts, ­ fibroblastic activity
•Eddies (Eddy) – circular current of fluid often moving
against the main flow
–Flows around the cell membranes & its organelles
–Flow of bubbles in stream cause change in cell membrane
permeability

28. Clinical Applications – Soft Tissue
•Stimulates release of histamine from mast
cells
–May be due to cavitation & streaming
–­ transport of calcium ions across membrane that
stimulates histamine release
–Histamine attracts leukocytes, that clean up
debris, & monocytes that release chemotactic
agens & growth factors that stimulate fibroblasts
& endothelial cells to form a collagen-rich, well-
vascularized tissue

29. Clinical Applications – Soft Tissue & Plantar
Warts
•Pitting edema - ­ temp. makes thick edema
liquefy thus promoting lymphatic drainage
•­ fibroblasts = stimulation of collagen
production = gives CT more strength
•Plantar Warts - 0.6 W/cm
2
for 7-15 min.

30. Clinical Applications – Scar Tissue, Joint
Contracture, & Pain Reduction
•­ mobility of mature scar
•­ tissue extensibility
•Softens scar tissue
•­ pain threshold
•Stimulates large-diameter myelinated n. fibers
•­ n. conduction velocity

31. Clinical Applications
•Chronic Inflammation - Pulsed US has been
shown to be effective with ¯ pain & ­ ROM
–1.0 to 2.0 W/cm
2
at 20% duty cycle
•Bone Healing – Pulsed US has been shown to
accelerate fracture repair
–0.5 W/cm
2
at 20% duty cycle for 5 min., 4x/wk
–Caution over epiphysis – may cause premature
closure

32. Treatment Duration & Area
•Length of time depends on the
–Size of area
–Output intensity
–Goals of treatment
–Frequency
•Area should be no larger than 2-3 times the surface area
of the sound head ERA
•If the area is large, it can divided into smaller treatment
zones
•When vigorous heating is desired, duration should be
10-12 min. for 1 MHz & 3-4 min. for 3 MHz
•Generally a 10-14 day treatment period

33. Thermal
Applications

35. Treatment Goal & Duration
•Adjust the intensity & time according to
specific outcome
•Desired temp.  ¸ /min. = treatment min.
–Ex. For 1.5 W/cm
2
: 2°C ¸ .3°C = 6.67 min.

36. Phonophoresis
•US is used to deliver a medication via a safe, painless,
noninvasive technique
•Opens pathways to drive molecules into the tissues
•Not likely to damage or burn skin as with iontophoresis
•Usually introduces an anti-inflammatory drug
•Preheating the area may enhance delivery of
medication
–Encourages vascular absorption & distribution of meds.
•Some medications are poor conductors

37. Phonophoresis
•Factors affecting rate of medication diffusion
–Hydration – higher water content = skin more penetrable
–Age – better with younger ages
–Composition – better near hair follicles, sebaceous glands &
sweat ducts
–Vasularity – higher vascular areas are better
–Thickness – thinner skin is better
•Types of medications
–Corticosteroids – hydrocortisone, dexamethasone
–Salicylates -
–Anesthetics - lidocaine